This is the Rear Cover for the Ofna Hyper Mach .28 Nitro Car Pull-Start Engine, OFNG5320. FEATURES: For use if engine is converted to starter box operation INCLUDES: Rear Cover with rubber O-ring for the Ofna Hyper Mach .28 Nitro Car Engine REQUIRES: Removing pull-starter assembly and replacing with this back cover SPECS: Length: 1.2" (30.6mm) Width: 1.2" (30.6mm) Thickness: 0.71" (18mm) jxs 5/05/06 ir/jxs